The present invention generally relates to an automotive vehicle including a slip control for effecting periodic variation in engine output in order to suppress slip which driving wheels undergo, and more particularly to a shift control for an automatic transmission of such automotive vehicle.
It is known from Japanese Patent Application Kokai (JP-A) 62-45944 to effect periodic variation in engine output by controlling second throttle valve disposed in series in an intake passage with a first throttle valve operatively connected with an accelerator pedal in order to suppress slip which driving wheels undergo.
A shift control for an automatic transmission is known where a throttle opening degree of the throttle valve which is operatively connected with an accelerator pedal is measured and a revolution speed of the transmission output shaft is measured, and they are used to determined an appropriate speed or gear position. If this shift control is used in conjunction with the above-mentioned slip control, there occurs a problem that undesired periodic shift in speed position might take place during the slip control, since during the slip control the revolution speed of the transmission output shaft deviates greatly from the actual vehicle speed when the driving wheels undergo slip.
An object of the present invention is to improve the shift control to adapt well to the slip control without any change in sensors which the shift control relies on.